Intravaginal Progestagen Research Articles

In vitro effects of different doses of FSH on oocyte maturation and embryo development

The purpose of this study was to assess the ovulatory response and embryo production after repeated superovulation of selected high-prolificacy Rasa Aragonesa ewes at the end of their reproductive life. A total of 211 superovulatory treatments were performed during the breeding seasons of 3 consecutive years. Ewes were given the same gonadotrophin treatment up to three times at intervals of at least 50 days. They were synchronized with intravaginal progestagen sponges and treated with ovine follicle stimulating hormone (oFSH) equivalent to a total dose of 176 NIH-FSH-S1 units in eight decreasing doses administered at 12-h intervals from 72 h before sponge removal. Embryos were recovered by laparotomy 7 days after the onset of oestrus. There was no effect of year on the superovulatory response as measured by the percentages of ewes in oestrus (80%) or ovulating (67%). An average of four freezable embryos (compacted morulae and blastocysts) were recovered at each treatment from the 141 ovulating ewes, with no significant differences amongst years, although the process seemed to be less efficient after the third treatment than after the first or second ones (2.4 vs. 4.1 (P<0.10) or 4.5 (P<0.05) freezable embryos, respectively). This was primarily attributable to a lower ovulation rate (three fewer corpora lutea; P<0.10). Results indicate that the methodology used in the present study could be an efficient and inexpensive way to obtain high-quality embryos from selected high-prolificacy animals before culling.

The Effect of Concentrate Supplementation and Prolificacy on Hay Intake and Performance of Pregnant Manchega Ewes

Factors influencing voluntary forage intake in ewes during the last two months of gestation are not sufficiently documented. The effects of hay quality and level of concentrate were studied by Orr and Treacher (1984) but other factors such as prolificacy or level of body reserves are poorly understood (Theriez et al., 1987). Furthermore most of the results come from animals kept in individual pens abolishing the effect of behavioural interactions. The purpose of the present experiment was to examine the effect of the number of gestated lambs and level of concentrate on voluntary intake of hay by ewes kept in a group.A flock of 120 multiparous Manchega dairy ewes were synchronised using intravaginal progestagen and injected with 400 IU of PMSG (Chronogest, Intervet). After ultrasonic pregnancy diagnosis at 60 d after mating (Toshiba Sonolayer, Mod.Sad-32B, 5.0 MHz), two groups of 30 twin or single pregnant ewes were selected and distributed in a factorial design 2x2x3. Factors were number of foetus (S = l, T=2) and level of concentrate (H=600 g/d, L=300 g/d) with 3 replicates of 5 ewes each.

Effects of hormonal treatment and interval between treatment on follicle development in calves

In order to study the reproductive response to a synchronising hormonal treatment, oestrus, fertility and litter size were compared among 44 Queue Fine de l’Ouest (QFO) ewe lambs and 44 D’Man×QFO contemporaries run in a single flock under natural grazing conditions. Within breed, animals were divided into two groups (balanced for live weight) of 22 ewes, each induced to breed at 9 months of age after being treated with intravaginal progestagen and 200 or 400 IU PMSG, respectively, in groups 1 or 2. Throughout the 45 days mating period, ewes in oestrus were mated by Noire de Thibar rams. The hormonal treatment was effective in inducing oestrus in over 90% of the ewes. At the induced ovulation, the breed and the dose of PMSG did not affect either the number of animals exhibiting oestrous behaviour, or allowing mating. After the mating period, breed had a significant effect on fertility, with lambing rates of 93 and 66% for ewes of the D’Man×QFO and QFO breeds, respectively. Breed also significantly affected the proportions of females lambing when conception occurred at the induced oestrus. Though not significant, ewe lambs of both breeds receiving 400 IU PMSG produced 16% more lambs than those treated with the lower dose of 200 IU. With a dose of 200 IU PMSG, ewe lambs of the D’Man×QFO breed tended to yield a higher litter size than the QFO contemporaries (1.2±0.40 vs. 1.1±0.26). Globally, the results showed that attempts to breed from ewe lambs of the D’Man×QFO breed under the conditions described here are likely to lead to more satisfactory conception rates than in the case of the autochthonous QFO breed.

Effects of PMSG and ram contact on the reproductive performance of progestagen-treated ewes during breeding and anestrous seasons

The objective of this study was to evaluate the efficacy of combinations of PMSG treatment and ram contact on the reproductive performance of progestagen-treated ewes during three different times of the year, Febraury (early anestrus), July (late anestrus) and October (breeding season). A total of 109 multiparous Dorset ewes was used. Ewes were treated with intravaginal progestagen pessaries for 12 days, injected with 500 IU PMSG at pessary removal and either isolated from rams prior to mating ( n = 12, February; n = 12, July; n = 8, October) or exposed to rams during pessary treatment ( n = 17, February; n = 12, July; n = 8, October). A third treatment group ( n = 18, February; n = 6, July; n = 8, October) received pessaries and ram exposure but no PMSG. An additional treatment of progestagen pessaries alone was included in October ( n = 8). There were no differences among treatments in their ability to induce estrus at different times of the year, but incidence of estrus tended ( P < 0.10) to be lower for PMSG treatment during the July breeding. During February, the use of pessaries with PMSG treatment increased ( P < 0.05) conception and lambing rates, whereas ram contact was without any beneficial effects. The trend was reversed during July breeding, when ram contact increased ( P < 0.05) fertility of progestagen-treated ewes compared with other treatment combinations. Pessaries alone were sufficient to attain acceptable levels of fertility and fecundity in October.

Fertility of superovulated ewes after intrauterine or oviducal insemination with low numbers of fresh or frozen-thawed spermatozoa.

Two experiments investigated the effects of number of spermatozoa inseminated and time and site of insemination of fresh and frozen-thawed semen on fertility in Merino ewes treated with intravaginal progestagen pessaries and a combination of pregnant mare serum gonadotrophin and follicle stimulating hormone. In Experiment 1, ewes were inseminated in the uterus or oviducts with totals of 10(4), 10(5), 10(6) or 10(7) fresh spermatozoa 44 or 68 h after pessary removal. Ova recovered 48 h later were classified as fertilized if they had cleaved. Proportion of fertile ewes (ewes with fertilized ova per ewes inseminated) and fertilization rate of ova (ova fertilized per ova recovered) were higher for inseminations 44 h (63% and 45%) than 68 h (38% and 19%) after pessary removal (P < 0.001). More ewes were fertile after oviducal (61%) than after intrauterine insemination (39%; P < 0.05), and with high (10(6) and 10(7)) than with low (10(4) and 10(5)) doses of spermatozoa for intrauterine (54% v. 24%; P < 0.05) but not for oviducal inseminations (63% v. 59%). Fertilization of ova was better after oviducal than after intrauterine inseminations (44% v. 22%; P < 0.001), and with high than with low doses of spermatozoa (45% v. 21%; P < 0.001). In Experiment 2, ewes were inseminated with 10(5), 5 x 10(5) or 10(6) total fresh or frozen-thawed spermatozoa in the uterus or oviducts, 44 h after pessary removal.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of ovulation, storage of semen, and artificial insemination of fibre-producing goats in Australia: a review

Artificial insemination (AI) allows individual bucks to be exploited widely and so is a potentially useful tool for the rapid genetic improvement of fibre goats. In Australia, where there is a desire by farmers to improve the productivity of their goats, AI may best be adopted under extensive grazing conditions using control of ovulation to allow efficient and accurate timing of the deposition of frozen-stored semen. Although ovulatory activity is influenced by the manipulation of environmental factors, the time of ovulation is synchronised most accurately by the combined use of intravaginal progestagens and pregnant mares' serum gonadotrophin. However, the costs of these exogenous hormones remain high, which justifies investigation of alternative methods to control ovulation. Bucks show strong seasonality in the quality and quantity of their sperm production, and so there is limited time in which semen may be collected for storage and AI, but this can be extended by optimising nutrition and management. There appears to be no improvement in the fertility of stored semen when seminal plasma, which contains egg yolk coagulating enzyme, is removed and an extender containing only a low concentration of egg yolk is used for dilution. Simple methods have been developed for 1-step dilution and freezing of buck semen. However, the post-thawing viability of spermatozoa frozen in pellets on dry ice is higher than for semen frozen in straws in liquid N2 vapour, although straws are preferred for commercial trade. For frozen-thawed semen, fertility after laparoscopic insemination is high, whereas the fertility after cervical insemination is considerably lower but improves by the deeper placement of semen into the reproductive tract. Does are best inseminated 5-10 h before the expected time of ovulation. A dose as low as 1 x 106 motile spermatozoa may be used for laparoscopic insemination of thawed semen that was previously diluted at rates (semen: diluent) of 1:2 to 1:23. However, for the cervical method, a low dilution rate of 1:2 allows a sufficiently small, highly concentrated dose of at least 120 x 106 motile frozen-thawed spermatozoa t o be deposited into the reproductive tract of the doe. Cervical insemination is cheaper and simpler than the laparoscopic method, and this warrants the development of an improved technique for the consistent, deep deposition of frozen-thawed semen through the cervix in a high proportion of does.

Ovarian and endocrine responses of Merino ewes to treatment with PMSG and/or FSH-P

An experiment was conducted to investigate the effects of different superovulatory regimes, including pregnant mare serum gonadotrophin (PMSG) and follicle-stimulating hormone (FSH-P) on steroidogenesis, oestrus, ovulation and premature luteal regression in sheep. Thirty mature Merino ewes were treated in the breeding season with intravaginal progestagen pessaries and 1200 IU PMSG (Group 1), 15 mg FSH-P (Group 2) or a combination of 700 IU PMSG and 11 mg FSH-P (PMSG/FSH-P; Group 3) to induce superovulation. After treatment with FSH-P alone, the incidence of oestrus was lower than after treatment with PMSG alone (6/10 vs. 10/10, P < 0.05) and the incidence of ovulation was lower than after treatment including PMSG (7/10 vs. 20/20, P < 0.05). However, there were no differences in the mean time to onset of oestrus (24.7 ± 2.3 h after pessary withdrawal) or the time to onset of ovulation (48–54 h after pessary withdrawal) between the treatment groups. The total ovarian response (corpora lutea + large follicles) was higher ( P < 0.05) following stimulation with PMSG alone (17.1 ± 1.9) than with FSH-P (8.3 ± 12.5). However, the numbers of corpora lutea present on Day 6 (Day 0 = pessary withdrawal) were not affected by the exogenous gonadotrophin treatment (PMSG, 11.4 ± 1.8; FSH-P, 7.2 ± 2.5; PMSG/FSH-P, 11.1 ± 2.1; not significant). The mean pre-ovulatory peripheral plasma peak level of oestradiol-17β (E 2) per follicle was higher following treatment with PMSG than with either of the other two regimes (PMSG, 23.2 ± 0.8 pg ml −1; FSHP, 10.8 ± 0.6 pg ml −1; PMSG/FSH-P, 13.9 ± 0.4 pg ml −1; P < 0.05). Moreover, E 2 peaked earlier in the ewes treated with PMSG than with FSH-P or PMSG/FSH-P (7.6 ± 2.1 h vs. 33.7 ± 1.5 h and 24.8 ± 0.5 h respectively; P < 0.01). There were no differences detected in the peak levels of luteinizing hormone (LH) (8.6 ± 1.1 ng ml −1) or the mean time to LH peak (32 ± 1.4 h) between the ewes treated with the different exogenous gonadotrophins. Three ewes (one treated with PMSG alone and two with PMSG/FSH) had premature luteal regression by Day 6. In each case, a secondary peak of E 2 secretion was observed 36–44 h after pessary withdrawal. These ewes each displayed a second oestrus on Days 5–6 and a mild superovulatory response at this oestrus. It is concluded that in sheep PMSG is highly steroidogenic in comparison with FSH-P. A combination of moderate doses of PMSG and FSH-P is a suitable superovulation regime for Merino ewes as it induces a consistently high superovulatory response without the secretion of excessive E 2 levels. Perturbation of the periovulatory endocrine events may result in premature luteal regression.

Different synchronization techniques in Boer goat does outside the normal breeding season

Synchronization techniques outside the normal breeding season were evaluated on 85 Boer goats with intravaginal progestagen sponges, sponges plus prostaglandin, and two injections of prostaglandin, with or without 500 IU PMSG. Oestrous response following the double prostaglandin injection regime was significantly ( P < 0.01) lower than in the intravaginal sponge and sponge plus protaglandin groups (with and without exogenous PMSG). The PMSG led to a higher ( P < 0.01) oestrous response in goats treated with intravaginal sponges only (100.0% vs. 53.3%). Administration of 500 IU PMSG led to a shorter time interval ( P<0.01) from cessation of treatment to the onset of oestrus in the intravaginal sponge and sponge plus prostaglandin groups (40.0 vs. 72.1 hr and 39.3 vs. 71.3hr, respectively). Time interval from treatment to the LH peak was shorter ( P<0.01) in the groups (excluding the double injection prostaglandin groups) receiving 500 IU PMSG, with no significant difference between the two intravaginal sponge treated groups. No significant differences in the time interval between LH peak and onset of the oestrous period was recorded between treatment groups. There was no significant difference in fertility between the intravaginal sponge and sponge plus prostaglandin groups (73.3 vs. 66.7% with PMSG and 53.3 vs. 60.0% without PMSG). Intravaginal sponge and sponge plus prostaglandin techniques (with PMSG) are effective as synchronizing agents outside the breeding season in Boer goat does. The double prostaglandin injection regime on the other hand proved ineffective outside the breeding season.

Effect of rumen degradable bolus containing melatonin or progestagen pessary plus pregnant mare serum gonadotropin on estrus response and lambing rate in ewes

Two practical regimens designed to induce estrus and ovulation in ewes in late anestrus were compared. Forty ewes were given a soluble glass rumen bolus containing 150 mg melatonin on July 9 and were joined with two vasectomized rams on July 23 and with three fertile rams on August 6. A second group of 40 ewes was treated with an intravaginal progestagen pessary (60mg medroxy-progesterone acetate) on July 23. Following pessary removal after 12 d, ewes were given 750 IU of pregnant mare serum gonadotropin (PMSG). Five fertile rams were joined with these ewes 48 h after progestagen removal. Melatonin concentrations were determined in single blood samples collected in early afternoon of July 21. Mating dates, lambing dates and litter sizes were recorded. Date of mating was significantly later in ewes treated with melatonin compared with those treated with progestagen plus PMSG (P<0.0001). All ewes given melatonin were mated within 4 wk, and those on progestagen plus PMSG treatment within one day of fertile ram introduction. Thirty-four ewes (85%) allocated to melatonin treatment and 36 (90%) allocated to progestagen plus PMSG treatment lambed (P>0.05). Mean (±SEM) lambing date was later in melatonin-treated ewes (January 17±1.2 d) compared to those given progestagen plus PMSG (December 30±0.6 d; P<0.0001). Mean litter size was lower in melatonin-treated ewes (1.5±0.1) compared with those given progestagen plus PMSG (2.0±0.1; P<0.001). Plasma melatonin concentrations indicated that 9 of 40 ewes treated with melatonin had circulating melatonin concentrations of less than 16 pg/ml. It is concluded that under conditions that existed in this experiment, treatment with progestagen plus PMSG in late anestrus resulted in more synchronous mating and lambing and a higher litter size than that following administration of a soluble glass rumen-degradable bolus containing melatonin.

Ovarian and endocrine responses of merino ewes following treatment with PMSG and GnRH or PMSG antiserum

Forty-eight mature merino ewes were treated in the breeding season with intravaginal progestagen pessaries and 1200 IU pregnant mare serum gonadotrophin (PMSG). The ewes were randomly allocated into four treatment groups. Group 1 served as controls; Groups 2 and 3 received an i.v. injection of 100 μg of synthetic gonadotrophin releasing hormone (GnRH) 12 or 24 h after pessary withdrawal (PW), respectively; and, Group 4 received a s.c. injection of 2 ml of ovine PMSG antiserum (A/S) 24 h after PW. Injecting GnRH at 12 h, advanced the time to onset of ovulation, but reduced the total follicular response (corpora lutea plus large follicles) and numbers of corpora lutea. The total follicular response was similar in Groups 1, 3 and 4, but the numbers of corpora lutea were higher in ewes injected with GnRH or PMSG A/S 24 h after PW compared with control animals. The mean peripheral plasma peak levels of oestradiol-17β (E 2) per follicle and progesterone per corpus luteum were reduced following treatment with GnRH or PMSG A/S. Moreover, treatment with GnRH advanced the time to and magnitude of the luteinising hormone peak. It was concluded that treatment with GnRH or PMSG A/S at the appropriate time may improve the superovulatory response of ewes to PMSG by increasing the proportion of developing follicles which ovulate. These treatments may also have beneficial effects on the fertility of superovulated ewes by limiting peri-ovulatory oestrogen secretion.

Effect of progestagen treatments on the incidence of oestrus and pregnancy rates in ewes

In experiment 1, a 4 × 3 × 2 factorial design was used to examine the effect of intravaginal progestagen (60 mg medroxyprogesterone acetate; 30 mg fluorogestone acetate; 500 mg progesterone or a controlled internal drug release device with 12% w/w (0.4 g) progesterone), pregnant mare serum gonadotrophin (PMSG) dose level (500, 750 or (1000) IU) and mating management systems (hand or paddock) on the induction of oestrus and pregnancy in 247 anoestrous ewes and 100 ewes during the breeding season. The intravaginal treatments employed in the anoestrous group did not affect oestrous response (96%), proportion of ewes lambing (72%) or litter size (1.74). When applied in cyclic ewes, a higher proportion ( P < 0.025) of ewes lambed to the controlled oestrus following synthetic progestagens (84% v 62%). Increasing PMSG from 500 to 1000 IU depressed litter size in cyclic animals. There were indications in the anoestrous ewes that the minimum effective dose of PMSG may be higher when combined with progesterone treatments, rather than with synthetic progestagens. Mating method did not affect the percentage of ewes mated or lambing, although there were indications that the paddock mating system resulted in a higher litter size. In experiment 2, 854 lowland ewes, on 10 commercial farms, were synchronised using either synthetic (FGA; n = 426) or natural (CIDR; n = 428) progestagens in late July. A lower proportion ( P < 0.05) of ewes treated with CIDR lambed to the induced oestrus (67% v 77%). There were no treatment differences in litter size. Results of these experiments suggest that synthetic progestagens are likely to be more successful than progesterone, particularly in the breeding season, in obtaining high pregnancy rates.

Fertility of superovulated ewes following intrauterine or oviducal insemination with fresh or frozen-thawed semen

Two experiments were conducted with mature Merino ewes to investigate the effects of time and site of insemination of fresh and frozen-thawed semen on the fertility of superovulated ewes. In Experiment 1, each ewe was treated with an intravaginal progestagen sponge and PMSG and/or FSH. They were inseminated in the uterus with fresh or frozen-thawed semen (approximately 100 x 10(6) motile sperm) at 24, 44 or 64 h after sponge withdrawal. Ova were recovered at 88 h after sponge withdrawal and classified as fertilized if they had pronuclei or had cleaved. Mean fertilization rates of recovered ova were 60.0, 93.7 and 87.8% for fresh semen and 46.1, 98.2 and 26.1% for frozen-thawed semen at each of the insemination times (24, 44 and 64 h) respectively. Overall, fertilization rates were higher for fresh semen than for frozen-thawed semen (P less than 0.01), but there was an interaction with time of insemination (P less than 0.01). Following insemination with frozen-thawed semen at 64 h, only 61% of the fertilized ova developed to the 2- to 4-cell stage by the time of embryo recovery; this was less than in any of the other groups (P less than 0.05). In Experiment 2, ewes were inseminated with 100 x 10(6) motile fresh or frozen-thawed semen in the uterus or in the oviducts at 64 h after sponge withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Superovulation of Merino ewes with an ovine pituitary follicle stimulating hormone extract

In order to investigate the effectiveness of ovine FSH as a superovulatory gonadotrophin in sheep, three batches (oFSH-1, oFSH-2 and oFSH-3) of crude follicle stimulating hormone (FSH) extracts were prepared from ovine pituitaries by protein fractionation. The extracts were characterized in radioimmunoassays (RIA), radioreceptor assays (RRA) and bioassays. A FSH:LH (luteinizing hormone) ratio of 1:0.71 and 1:0.18 was calculated from oFSH-1 in RIA and RRA respectively. oFSH-1 was more potent than NIH-oFSH-S12 in RRA, with a potency ratio of 1:0.65 calculated at 50% binding. In mouse bioassay, oFSH-2 was effective in inducing folliculogenesis. The potency of oFSH-3 as an ovarian stimulatory hormone was tested in a field trial on sheep. Thirty-one mature Merino ewes were treated in the breeding season with intravaginal progestagen pessaries and 6, 12 or 24 mg doses of oFSH-3 were injected twice daily for 3 days (n = 10 or 11). Each ewe was inseminated in the uterus with fresh semen 24 h after pessary withdrawal. Ova or embryos were recovered by mid-ventral laparotomy 6 or 7 days after pessary withdrawal. The dose of oFSH-3 had a significant effect on the ovulatory response (P less than 0.01); the mean ovulation rates were 1.5 +/- 0.2, 12.6 +/- 2.8 and 13.1 +/- 2.9 following injection with 6, 12 or 24 mg of the gonadotrophin respectively. The dose of the gonadotrophin injected had no effect on the mean percentages of ova recovered or fertilized. The overall ova recovery and fertilization rates (%) were 67.8 +/- 6.4 and 92.2 +/- 5.1 respectively. (ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pregnant mare serum gonadotrophin (PMSG) and route of administration after progestagen treatment on oestrus and LH secretion in the Boer goat

During the breeding season, 94 mature Boer goats were treated with intravaginal progestagen sponges (MAP, 60 mg) for a period of 14 days. Upon sponge withdrawal, goats received 300 i.u. PMSG either subcutaneously ( n = 32) or intramuscularly ( n = 30). A control group was not treated with PMSG ( n = 32). Administration of 300 i.u. PMSG at sponge withdrawal had no significant effect on the number of animals exhibiting oestrus in each group. Interval from sponge withdrawal to commencement of oestrus was shorter for intramuscular ( P < 0.01) and subcutaneous ( P < 0.05) PMSG-treated groups than controls, with the route of PMSG administration not having a significant effect. Mean duration of induced oestrus was significantly shorter ( P < 0.05) in the control group. The interval from onset of oestrus to the occurrence of the preovulatory LH peak was shorter ( P < 0.05) in the group receiving PMSG subcutaneously.

The effect of progestagen type, PMSG dosage and time of ram introduction on reproductive performance in ewe lambs

One hundred and fifty-four March born lowland ewe lambs were allocated to a 2 × 2 × 2 factorial experiment. In October, intravaginal progestagen sponges, containing either 60 mg medroxprogesterone acetate (MAP) or 30 mg fluorogestone acetate (FGA), were inserted for 12 d. Following progestagen withdrawal, each ewe received an intramuscular injection of either 0 or 400 IU pregnant mare serum gonadotrophin (PMSG). Fertile rams were joined 36 or 48 h later, at a ratio of 1:6. The progestagen type employed did not affect conception rate or litter size. PMSG resulted in more active mating activity within the first 4 h of ram introduction (P < 0.01), but there was no difference in lambing rate, and litter size was only slightly increased. When rams were introduced at 36 h, mating took place over a longer period (P < 0.005), pregnancy rate was increased (P < 0.01) and litter size was lowered (P < 0.05).

Evidence for prostaglandin involvement in early luteal regression of the superovulated nanny goat (Capra hircus).

Feral does of various ages were treated with intravaginal progestagen sponges for 16 days to synchronize oestrus. On Day 2 before sponge removal the goats were given 1200 i.u. PMSG to induce superovulation: 6 of the goats were also injected every 12 h with flunixin meglumine, a prostaglandin (PG) synthetase inhibitor, from Day 3 to 7 of the synchronized oestrous cycle. Jugular blood samples were collected from all females into heparinized syringes at daily intervals over the 2 days before sponge removal, twice daily for the next 2 days, then at hourly intervals from 09:00 to 17:00 h for 2 days and then twice daily for a further 2 days, for measurement of plasma progesterone and the PGF metabolite 13,14-dihydro-15-keto-PGF (PGFM) by radioimmunoassay. Intermittent surges in plasma PGFM concentrations were observed in hourly samples collected from 4/4 untreated females but in only 2/6 of the inhibitor-treated females (P less than 0.05), and the peak plasma PGFM concentrations were reduced in these 2 inhibitor-treated goats compared with the control goats. The corpora lutea (CL) of the inhibitor-treated females appeared to be functional as indicated by the plasma progesterone profile and endoscopic examination of CL. In the control females, however, there was evidence of premature regression of CL. These results suggest that the premature release of PGF-2 alpha may be the cause of premature regression of CL in nanny goats induced to superovulate.

Comparison of a controlled internal drug release device containing progesterone with intravaginal medroxyprogesterone sponges for estrus synchronization in ewes

Intravaginal progestagens have been used for many years to synchronize estrus in ewes. This experiment compares two such treatments: 60 mg medroxyprogesterone (MAP) sponges and a controlled internal drug release (CIDR) device containing 366 mg natural progesterone. No pregnant mare serum gonadotropin (PMSG) was used. Treatments were given to groups of 10 to 20 ewes for 14 d at various times during breeding season. Rams were introduced 1 d after treatment removal, and day of mating was recorded. Rams were removed after 3 d. Pregnancy was checked with ultrasound 60 d later. There was no diffeence in rate of marking by rams (88%) or pregnancy rate (57%) between treatments. Ewes receiving CIDR devices showed estrus earlier and with closer synchrony (P < 0.01). The CIDR device is comparable to the MAP sponge for estrus synchrony during the breeding season, and reasonable fertility can be achieved without the use of PMSG.

Synchronization of oestrus in sheep: The use of controlled internal drug release (CIDR) dispensers

The use of the CIDR (controlled internal drug release) dispenser as a progestagen-synchronizing agent was evaluated in 37 Karakul ewes during the breeding season, using the intravaginal progestagen sponge as a control (30 ewes). Although there was no significant differences in oestrous response, following intravaginal insertion for 14days, between these two progestagen devices, the time from device withdrawal to the onset of the induced oestrous period (31,2 vs 62,5 h) and the duration of the induced oestrous period (32,7 vs 47,4 h) was significantly (P<0,01) shorter in the CIDR dispenser group. The mean time from device withdrawal to the serum preovulatory LH peak and the interval from the onset of oestrus to the pre-ovulatory LH peak was significantly (P<O,Ol) earlier in the CIDR dispenser group (28,0 vs 78,0 hand 5,3 vs 17,3 h respectively). No significant difference in the serum progesterone concentrations was noted between the two groups. No significant difference in reproductive performance was obtained with conception, lambing rates and fecundities of 72,2 vs 79,3%; 75,0 vs 89% and 103,8 vs 113,0% for the dispenser and sponge treatment groups respectively. Results confirm the potential of the CIDR dispenser as an efficient synchronizing agent and the more concentrated synchrony obtained makes it ideal for fixed-time insemination.

Effects of active immunization against androstenedione on ovulation rate and fecundity in Galway and Finnish landrace sheep

Galway and Finnish Landrace ewes were immunized with an androstenedione protein conjugate (Fecundin, trademark of Glaxo Group Ltd.) on two occasions 30 days apart at the beginning of the breeding season. All sheep were treated with intravaginal progestagen sponges to synchronize cycles and exposed to rams for 6 weeks. The antibody titre to androstenedione, plasma androstenedione concentrations, display of oestrus, ovulation rate and litter size were determined. The results were compared with those for non-immunized animals and, in the case of the Galway breed, with ewes given 750 i.u. PMSG at the time of sponge removal. Over 98% of all ewes were mated within 30 days of sponge removal, but immunized ewes were delayed in their expression of oestrous cycles after withdrawal of progestagen treatment. The proportion of ewes mated that ultimately lambed was similar for all treatments, although during the first 5 days after sponge removal the conception rate was lower in immunized ewes. The mean ovulation rates for control, immunized and PMSG-treated Galway ewes were 1.75, 2.52 and 2.05, respectively; the corresponding values for litter size at birth were 1.48, 1.89 and 1.53, respectively. Comparison of the effects of immunization in the Galway and Finnish Landrace breeds indicated that ovulation rate increased in response to treatment in both breeds. Although litter size also increased in the Galway there was no evidence for a similar effect in the Finnish Landrace breed. Plasma concentrations of androstenedione were significantly higher following immunization in Galway than in Finnish Landrace ewes. There was an association between high antibody titres to androstenedione and the reduction in behavioural oestrus and conception rate immediately after sponge removal. The implication of this effect in sheep management is to initiate the immunization earlier in the season so that the introduction of the ram can take place 3–4 weeks after the booster injection when as these data have shown, the fertility of the ewes is similar to untreated ewes but the fecundity is higher.

Ovulation and LH secretion in the goat after intravaginal progestagen sponge-PMSG treatment.

The time and rate of ovulation, and preovulatory release of LH were examined in Angora goats after treatment with progestagen-impregnated intravaginal sponges with or without PMSG during the anoestrous and breeding seasons. The administration of PMSG was necessary to stimulate a satisfactory ovulatory response in lactating and non-lactating females, and in the anoestrous and breeding seasons. Increasing doses of PMSG increased the ovulation rate in non-lactating goats and advanced the time of ovulation in lactating and non-lactating females. The advancement of time of ovulation and of the preovulatory LH surge was most pronounced when PMSG was administered 48 h before rather than at sponge removal.